The performance of a handgun is determined by the behavior of its constituent parts. The combination of these parts determines the guns weight, recoil, accuracy, cycle time, and so forth.
In competition settings the most important characteristics of the user are accuracy and cycle time. Accuracy is a measurement of the user's ability to place a bullet where intended, and cycle time is the time that elapses between the discharge of a round and the discharge of the subsequent round.
It is the communication between the gun and the user that largely determines the accuracy and cycle time of the gun. This communication occurs through the trigger; the only part of the gun that the user controls during normal use. Thus, alterations to the gun that result in changes to the feel and behavior of the trigger have significant effects on the user's perception of the gun's functionality, and ultimately the user's performance.
Furthermore, the user's awareness of the state of the gun is critical to its safe operation. The user must be able to feel when the gun is prepared to fire the next round to avoid accidental discharge.
But users often already own a gun, and do not wish to purchase a new and unfamiliar gun in order to achieve greater feedback.
What is needed is a collection of parts that can be added to an existing gun, the parts improving communication through the trigger, thereby increasing user accuracy, decreasing cycle time, and maintaining or improving safety.